Letter 7523

Chemical resistant protective tank coating 

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I am looking for a protective coating to apply on a koroseal lined chrome plating tank

Our Hard Chrome Plating Solution Tank is a, koroseal lined tank with a PVC bag liner. We do not want to continue using a PVC bag liner, for a variety of reasons.

I've read about spray applied Polyurethane Membrane chemical resistant protective coating being used for tank lining.

I would like to know if any body has any first hand knowledge of a product that can hold up and be applied without having to remove the tank.

Our current method is to remove and ship the tank 150 miles to get spark tested and re-korosealed.

Larry Lausin
Naval Aviation Depot, Naval Air Station - San Deigo, CA USA

I don't think you're going to find such a coating and think a better approach might be to find a lining service who is able to strip and Koroseal re-line in situ.

 
Ted Mooney, P.E. - finishing.com Inc. - Brick, NJ

Larry,

I'm sorry to say but I think that you are being led up the proverbial garden path. A coating is a coating is a coating, ie. it's an ultra thin membrane which, even were it made from pure tfe and IF tfe could be 'painted' on and IF it would stick/glue perfectly it would FAIL because sooner (probably) or later (less probable) it is going to get scratched and being an ultra thin coating you are now back at base one to the apparently damaged Koroseal lining.

You have two options, re-Koroseal or, if the tank is relatively small, consider please a dual laminate construction. A dual laminate in this case would consist of min. l/4" thick uPVC which has an outer reinforcement bonded to it of fibreglass. You will appreciate that any flexible liner is never, ever as chemically resistant as the pure material. I'd go a step further and demand that you either use a Trovidur or a Simona uPVC material, that all corners are bent (which means, too, forming the 4 bottom 3-part edge corners) and, of course, to have the final unit spark tested for weld integrity. Obviously this work has to be done by a kopasetic dual laminate fabricator, an ordinary fibreglass fabricator even if given a well made all-PVC tank could, in my experience, cause it to fail! Finally, as with a good Koroseal type liner, I'd want to see a 'plate' overlay over the air/liquid interface to prevent oxidization at this juncture. Yes, this has been done before ... even as far back as l969 on l5 foot dia. chlorate cell tanks for Hooker Chemical in Mississipi although now the bonding methods are vastly simplified. ... a Canadian world's first, by the way!

Cheers!

Freeman Newton
retired from the 'plastics' field - White Rock, British Columbia, Canada

We own a hard chrome plating job shop in the eastern part of Holland, and we were having the same problems with our coroseal linings. Two years ago, we were looking for an alternative and we came to a FRP lining which was specially designed to hold up against the very aggressive chromium chemicals. The lining we use is called "Fiberliner" and is developed by Innoplate International in Holland. We are very pleased with it. Up to now we don't see any corrosion for example at the line where the fluid and oxigen meet. It's also a very strong coating and it can be repaired without losing its quality.

Good luck.

Tim Jaarsma
Hardchroom Techniek Nederland - Hengelo, Overijssel, The Netherlands

Hi again, Re Tim Jarsma's FIBRELINER and his success ... ah, that's only over a very short time period and the KOROSEAL lining people (always a competitor of mine!) would, I'm sure, say that in normal circumstances their linings last 5 or so years. Hence a 2 year life span doesn't mean very much, does it? Further, I'm very sure that if someone (and I KNOW IT HAS BEEN DONE!) were to properly line a steel tank using a very good vinylester or polyester resin (Atlac, Derakane or Hetron), I'm sure that that lining would ALSO last 2 years, too, ... but not as long as Koroseal. Like everything else, it depends, too, on the quality of the fabrication work. Further, when it comes to very severe corrosion, fibreglass per se is NOT used! They do not have a homogenous structure like thermoplastics. But they are better in heat deflection than many thermoplastics and definitely much stronger than any thermoplastic and have a much lower coeff. of expansion ... the ideal, where practical, is the synergistic marriage of the two to form a so-called armoured or dual laminate plastic.

Cheers!

Freeman Newton
- White Rock, B.C. Canada

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